Membrane changes associated with neoplastic transformation will be defined in molecular terms and will be correlated with membrane and cell surface expression relative to differentiation and degree of malignancy. Special attention will be focused on the role of lysolecithins and lysolecithin-type cholinephospholipids derived from short-chain diols in various membrane, enzyme and cell processes, and on the controlling steps that maintain physiological levels of monochain phospholipids. The effects of lysolecithins and diol-derived phosphocholines will be studied in tumors grown in rodents and in cultivated Novikoff rat hepatoma cells, virally transformed Balb/c 3T3 A31 cells, cells from human tumors, and others, as well as in respective controls. The effect of monochain phospholipids on membrane and surface properties of normal and transformed cells will be defined in terms of their susceptibility to lysis, and in terms of membrane fluidity as expressed by 2H, and 13C and 31P relaxation measurements and fluorescence spectroscopy. Drug-mediated lecithin inhibition and lysolecithin stimulation will be evaluated as a means to affect cell surface properties and to possibly influence cancerous proliferation. The role of monochain phospholipid-cholesterol-lecithin interactions will be studied in biological and model membranes.